This invention relates to centering bells for bottle filling machines of the type which move up and down vertically on filler tubes.
A number of manufacturers make bottle filling machines in which a centering bell rides up and down the filler tube, supported by a bushing in the centering bell which slides on the filler tube. Typically, the filler tube has an enlarged tip at its lower end with a shoulder which is contacted by the lower end of the bushing when the bell drops to its lowest position. This prevents the bell from falling off the end of the filler tube.
The areas of contact between the bushing and tube tip are narrow circular flat areas, perpendicular to the long (vertical) axis of the filler tube. Repeated contact between the bushing and the tube tip causes wear on the contact areas. In some cases, with heavy centering bells on a high speed filler, this wear can be extreme, with worst cases having a bushing life of less than two weeks.
Canadian Pat. No. 983,446 of Alexander R. Duncan, issued Feb. 10, 1976, shows a bell of this type in FIGS. 1 and 2, which relate to admitted prior art for that patent. The invention of the patent (FIG. 3 thereof) eliminates the shoulder on the tip of the filling tube and secures the bell in the top position so that it does not move up and down. However, this obviously eliminates the desirable centering function of the bell when a bottle approaches and begins to encircle the filler tube.
FIG. 2 of Canadian Pat. No. 989,365 of Alexander R. Duncan, issued May 18, 1976, shows an arrangement in which the centering bell moves up and down on the filler tube but, instead of an enlarged tip at the end of the filler tube, he uses a collar 6 adjacent the upper end of the tapered tip of the filler tube. However, a clip such as disclosed by Duncan would be subject to high wear problems, just as would a shoulder at the top of the tip portion of the filler tube. In this patent, Duncan refers to modern filling machines as operating at high speeds of, e.g., within the range of 725-750 b.p.m. While such speeds may have been considered "high" when Duncan filed his patent application in 1974, some bottle filling machines now operate at speeds up to 1200 b.p.m. Thus, what Duncan considered high speed is now considered relatively low.
In today's high speed bottle filling machines it is more than ever necessary to guard against contact between a bottle and a filler tube which could chip or break the bottle or possibly damage the filler tube. Because of the high speed of the equipment there is little time for a bottle to be properly centered with respect to a filler tube. The arrangement of Duncan's above-mentioned Canadian Pat. No. 983,446 eliminated the initial centering action of the bell by securing it in position at the top of the filler tube. Even though he reduced the size of the tip of the filler tube, there is a danger of metal-to-glass contact, particularly in today's high speed filling machines.